1. Field of the Invention
The present invention relates to a method for the assembly of automotive vehicle bodies and a jig unit to be employed therefor.
2. Description of the Related Art
In assembling automotive vehicle bodies in a vehicle body assembly line, each of main floor panels, front vehicle bodies, rear vehicle bodies containing rear floor members, vehicle body side panels (consisting of side inner panels and side outer panels), roof panels (consisting of roof inner members and roof outer panels) and lid members such as side doors, bonnets and trunk lids are usually sub-assembled in corresponding subassembly lines, and they are supplied from the corresponding sub-assembly lines to the vehicle body assembly line. Further, in a stage of the vehicle body assembly line for assembling an under vehicle body section, a floor panel, a front vehicle body section and a rear vehicle body section are aligned and fixed to a carriage or carrier with plural aligning members and clamping units mounted thereto and the under vehicle body section is assembled by welding temporarily and thereafter by welding supplementarily or permanently.
The under vehicle body section loaded on the carriage or carrier is transferred to the stage for mounting the upper vehicle body sections, and the vehicle body side panels, the roof panel, etc. are mounted to the under vehicle body section. In mounting the vehicle body side panel, the roof panel, etc. to the under vehicle body section, they are aligned with the under vehicle body section on the basis of the reference surfaces of their outer panels with the aid of an exclusive aligning unit disposed in each of stations, they are fixed to the carriage or carrier, and they are welded temporarily and thereafter supplementarily or permanently. The under vehicle body section is then mounted to the upper vehicle body section. Front fenders and rear fenders are mounted to the vehicle body section in a stage for mounting the upper vehicle body section.
On the other hand, Japanese Patent Laid-open Publication (kokai) No. 64-1,667 discloses a holding unit for holding a partially mounted vehicle body section. The holding unit comprises a main frame and three pairs of inner upstanding frames. The main frame is supported horizontally by four column members disposed upstanding on the floor of a factory and further mounted to the two upstanding columns disposed on a single side so as to be movable vertically. The three pairs of the inner frames are mounted to the main frame in the positions corresponding to the position in the vicinity of a vehicle body cowl section, the central vehicle body portion and the rear vehicle body portion, respectively, so as to be openably movable in the transverse direction of the vehicle body. To each of the inner frames are mounted plural clamping units, tools and so on. The three pairs of the inner frames are inserted from top into the roof opening of the partially mounted vehicle body shell (looking like the left-hand and right-hand side inner panels being temporarily mounted to the under vehicle body section) by swinging a lower end portion of the main frame of the holding unit. Thereafter, the three pairs of the inner frames are expanded to approach an inner surface of the vehicle body shell, and the rest of the assembly operations is carried out with the aid of plural clamps, tools and so on.
Conventional methods for the assembly of automotive vehicle bodies suffer from various disadvantages because the panel members, such as vehicle body side panels, etc. are aligned on the basis of their outer panels with the aid of an exclusive aligning Jig. The outer panels are so curved and complex in outer shape, the error in shape becomes so large due to the influence of the return of the curvature of the outer panels to their original shape, and rigidity of the outer panels is so low that accuracy in alignment of the outer panel members is likely to become low. Further, the outer panel members vary in shape in accordance with models so that the exclusive aligning tools should be prepared for each of the models of automotive vehicles. In addition, the aligning jigs of plural kinds should be made ready for immediate use in each station and the aligning Jigs should be fastened to and detached from the vehicle body section plural times during mounting so that working efficiency may become low. On the other hand, as the main floor panel is mounted to the upper vehicle body section in an initial stage of the conventional vehicle body assembly line, a large-sized and multi-functional mounting Jig unit for mounting the vehicle body sections cannot be disposed within the mounting vehicle body section and operations for mounting various parts, units and accessories, such as seats, may become very difficult. Further, problems arise that inner members should be provided with a number of welding holes for welding the connections of the side inner panels, such as sub-assembled vehicle body side panels, and the roof inner panels, that efficiency in operation for welding the inner members may become low, as well as that the number of stations for operations for welding and connecting become greater and that the length of the stations become longer, because welding robots and so on are disposed outside the vehicle body sections which are being mounted and, as a result, because the vehicle body sections are subjected to welding only from outside.
In the vehicle body section assembly line using the holding unit as disclosed in Japanese Patent Laid-open Publication (kokai) No. 64-1,667, the holding unit is applied to at least the under vehicle body section which is temporarily mounted to the side inner panel. Hence, the step is required for temporarily mounting the under vehicle body sections to the side inner panels. In addition, brackets, stays, bolts and so on are required for temporarily mounting the under vehicle body sections to the side inner panels, so that the structures of the panel members may become complex. Further, the three inner frames of the holding unit are inserted into the vehicle body shell through a comparably small roof opening section thereof, so that an inner frame thereof cannot be made larger in size and multiple in function, thereby rendering operations laborious and less efficient.